Snap-action mechanism



Nov. 27, 1962 w. RIDDELL ETAL SNAP-ACTION MECHANISM Filed Sept. 16, 1960 United States atent fitice 3,665,644 SNAP-ACTEQN MECHANEM William Riddell, Whitley Bay, Northumheriand, and Brian Asthury Holden, Newcastlearpon-Tyne, England, assiguors to Burgess Products Qompany Limited, Hirschley, England Filed Sept. 16, 1960, Ser. No. 56,522 Claims priority, application Great Britain Sept. 18, 1959 8 Claims. (Cl. 74-100) This invention relates to snap-action mechanisms of the type having two movable arms connected to each other by a spring in such a manner that the arms and the spring are displaceable through an aligned attitude from which further displacement takes place as a snap movement occasioned by the resilience of the spring. A com mon use of such mechanisms, hereinafter referred to as mechanisms of the type described, is to control the operation of electric switches.

According to the invention, there is provided a snapaction mechanism of the type described in which the ends of the arms pivotally inter-engage. The term inter-em gage as used herein describes a construction in which one arm enters a recess in the other.

In the accompanying drawings PEG. 1 is an exploded perspective view, partly-cut away, of an electric switch embodying one form of snap-action mechanism according to the invention, and FIG. 2 is a fragmentary view of a modified detail.

Referring to FIGS. 1 and 2 of the drawings, two U- shaped arms ll, 21 (shown here in the aligned attitude) have a tension spring 1 connecting the bases of the Us. The tips of the Us are bent up at 35 and then down at 36 to present an inclined plane surface and are cut to approximatcly half-width to provide a prong, e.g. i2, 22; at each tip. The two prongs 12. of the arm 11, of which only one appears in the drawing, are on the outside of U, while prongs 22 of the arm 21 are on the inside, of which again only one can be seen. The two arms H and 2?. thus mutually inter-engage, the prongs i2 and 22 overlapping. The spring 1 holds the arms Ill, 21 in contact with each other along a line passing through the point 2 where the transverse edge of the cut-away on one arm rests on the inclined plane surface of the prong on the other, and this line of contact constitutes as axis about which each arm is pivotable.

The arms 11, 21 and the spring 1 together form a snapaction mechanism. The mechanism may be operated in any convenient way, e.g. by direct pressure on the arms at the prongs. actuator 3 slides in guides 4, and its movement is conveyed to the arm ill by means of lugs attached to the prongs and engaging clearance apertures in the actuator 3. In the example shown the lug 13 attached to the prong 12 engages an aperture 5 in the actuator 3. As shown, the aperture 5 is circular, but any suitably shaped aperture may be used. The actuator 3 may conveniently be a metal stamping. When the arm i1 moves in response to movement of the actuator 3, the arms ill, Z21 perform a mutual pivoting action about their line of contact through the point 2, extending the spring it until the spring and the arms are aligned at the deadcentre position. Immediately this position is passed, the spring 1 contracts and completes the pivoting action of the arms with a snap movement, regardless of further movement of the actuator 3. In order to reduce friction, the sides of the arms 11, 21 are relieved as shown at 32.

The guides 4 may conveniently be formed integrally with one part 6 of a housing comprising two similar or identical component parts, both made of insulating material. In the assembled switch, the part-housings are As shown in the drawing, a U-shaped held between the sides of a casing 7, which may be of metal, and secured by screws (not shown) passing through holes 8 in the housing-parts and apertures 9 in the casing. The casing may also have a screwing tag or tags, as at 10, and extensions to its top surface providing hole 23 for mounting screws.

Held in slots in the housing-part 6 and in the complementary part (not shown) are two pairs ofmetal stampings 14, 15; 24, 25, each bent at one end, which serve the double purpose of acting as electrical terminals and as stops for limiting the travel of the arms ll, 21. To ensure good electrical contact, studs 16 are provided on the underside of terminals 15, 25, on the upper side of terminals 14, 2d and on both sides of the arms 11, 21 at the bases of the Us The switch has two stable conditions, namely one in which the arms 11, 21 connect the terminals i4, 24, and another in which the arms connect the terminals 15, 25.

A return spring 17 is accommodated in a recess 18 in the part-housing 6 and in a corresponding recess in the other part-housing (not shown).

The actuator 3 may be operated by a plunger which engages the actuator directly. The drawing, however, show an alternative arrangement by means of which the switch is controlled by a cam. As indicated in the drawing, the actuator 3 has a pair of half-journals 19 to receive the reduced ends 20 of a roller 26. A lever 27 has, at one end, a pair of lugs 28 which engage slots 29 at one end of the part-housing 6. The other end of the lever .27 rests on the roller 26, and on the surface opposite that which rests on the roller, the lever 27 is provided with a wedge 3-0. In the assembled switch, the wedge 3% projects through a window 31 in the top of the casing 7. By suitably mounting the assembled switch, a cam may be arranged to engage the wedge 30 and thereby to control the switch.

In the modified form of pivotal connection shown in FIG. 2, the knife edge 33 on the arm 21 by entering a notch or re-entrant angle 34- on the arm 11 in which the notch is formed, inter-engages with the arm 1'1, lateral stability being provided by the actuator or housing as before.

What I claim and desire to secure by Letters Patent is:

l. A snap-action mechanism for an electric switch comprising two oppositely extending generally flat plates movable between two extreme positions and serving as contact arms, each of said plates having U-shaped arms placed with the end openings of each U next to each other to define an elongated opening bounded by the sides and base of the respective U-shapes, an end of each U-shaped arm extending first upwardly then downwardly, the downwardly extending end of each prong of both of said plates contacting the other in overlapping relation, a pivotal abutment extending laterally from the end of one arm, an abutment surface on the other arm on a common pivot line with said abutment, a tension spring placed in the opening between the respective U- shapes to urge the U-shaped arms together whereby snapaction of said pivotally movable arms is secured between the two extreme positions when said arms are moved through a position in which the arms and pivotal abutments are aligned, a part of a prong on each plate extending past the contacting prong of the other plate to reduce the friction in snap-action between said two positions.

2. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said arm being pivotally mounted on an actuating member slidably movable perpendicularly of said pivotal mounting, said arms being movable between two extreme positions, each arm having an inclined prongshaped end, each prong-shaped end engaging the other end in mutual overlapping relation, a pivotal abutment extending laterally from at least one prong on each arm and pivotally engaging an abutment surface on the other arm on a common pivot line and at least one tension spring connecting and urging said arms together whereby snap action of the pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

3. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said arm being pivotally mounted on an actuating member slidably movable perpendicularly of said pivotal mounting, said arms being movable between two extreme positions, each arm having an inclined prongshaped end, each prong-shaped end engaging the other end in mutual overlapping prong relation, a pivotal knife edged abutment extending laterally from at least one prong on each arm and pivotally engaging an abutment surface on the other arm on a common pivot line, and at least one tension spring connecting and urging said arms together whereby snap action of said pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

4. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said arm being pivotally mounted on an actuating member slidably movable perpendicularly of said pivotal mounting, said arms being movable between two extreme positions, each arm having an inclined prong-shaped end, each prong-shaped end engaging the other end in mutual overlapping prong relation, a pivotal knife edged abutment extending laterally from two prongs on each arm and pivotally engaging an abutment surface on the other arm on a common pivot line, and at least one tension spring connecting and urging said arms together whereby snap action of said pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

5. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said arm being pivotally mounted on an actuating member slidably movable perpendicularly of said pivotal mounting, said arms being movable between two extreme positions, each arm having an inclined prongshaped end, each prong-shaped end engaging the other end in mutual overlapping prong relation, a pivotal knife edged abutment extending laterally from two prongs on each arm and pivotally engaging an abutment surface on the other arm, said prongs when engaged defining a central U-shaped aperture in each arm, a tension spring in said U-shaped apertures, said spring connecting and urging said arms together whereby snap action of said pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

6. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said aim being pivotally mounted on an actuating member slidably movable perpendicularly of said pivotal mounting, said arms being movable between two extreme positions, each arm having an inclined prongshaped end extending from a reversely inclined portion of an otherwise fiat contact arm, each prong-shaped end engaging the other end in mutual overlapping prong relation, a pivotal abutment extending laterally from at least one prong on each arm and pivotally engaging an abutment surface on the other arm on a common pivot line, and at least one tension spring connecting and urging said arms together whereby snap action of said pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

7. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said arm being pivotally mounted on an actuatins member slidably movable perpendicularly of said pivotal mounting, said arms being movable between two extreme positions, each arm having an inclined prong-shaped end, each prong-shaped end engaging the other end in mutual overlapping prong relation, a pivotal abutment extending laterally from at least one prong on each arm and pivotally engaging an abutment surface on the other arm on a common pivot line, said abutment surfaces being disked and at least one tension spring connecting and urging said arms together whereby snap action of said pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

8. A snap-action mechanism for an electric switch comprising two oppositely extending plate-like free contact arms, one said arm being pivotally mounted on an actuating member slidably movable perpendicularly of said pivoral mounting, said arms being movable between two extreme positions, each arm having an inclined prong-shaped end, each prong-shaped end engaging the other in mutual overlapping prong relation, a pivotal abutment extending laterally from at least one prong on each arm formed by recessing the side of said prong and pivotally engaging an abutment surface on the other arm on a common pivot line, and at least one tension spring connecting and urging said arms together whereby snap action of said pivotally movable arms is secured between said two positions when said arms are moved through a position in which said contacts and pivotal abutments are aligned.

References Cited in the file of this patent UNITED STATES PATENTS 

